node: fix `fast` option.
node: fix `fast` option.

decentraland/decentraland-node,decentraland/bronzeage-node,decentraland/bronzeage-node,VidaID/bcoin,VidaID/bcoin,VidaID/bcoin,decentraland/decentraland-node,decentraland/bronzeage-node,decentraland/decentraland-node